Adhesive composition components such as base polymers, tackifiers, waxes, and oils are customarily provided as separate components for formulation into hot melt adhesive (HMA) compositions. HMA compositions for nonwoven applications are used for construction and lamination, e.g., to attach nonwoven and other components together and to adhere the layers of a material together. Nonwoven applications can include hygiene products such as baby diapers, adult diapers, incontinence products or devices, absorbent articles, panty liners, and sanitary napkins. In nonwoven applications, HMA compositions are sought that provide a desired combination of physical properties such as stable adhesion over time, indicative of broad application temperature ranges, and machine coatability. Machine coatability is a term well known in the art to refer to the robust application ability of an adhesive formulation on a substrate, via a machine, requiring only minimal adjustment of machine settings including machine speed and temperature. An adhesive formulation having good machine coatability can reduce time and therefore costs associated with the adhesive application process, because the adhesive formulation is versatile enough to be used on more than one machine without many adjustments of the machine settlings. Poor machine coatability can result in web breaks of the adhesive formulation during application of the adhesive at starting and stopping intervals of the machine, which can unfavorably impact line efficiency, and also result in increased down time and high costs. HMAs having stable and consistent adhesion over broad application temperatures are also generally sought for nonwoven construction and lamination applications.
Exemplary base polymer compositions and methods of making polymer compositions for HMA applications are disclosed in U.S. Pat. Nos. 7,294,681 and 7,524,910. Various polymers described in these patents and/or produced by the methods disclosed in these patents have been sold by ExxonMobil Chemical Company as LINXAR™ polymers.
International Publication No. 2013/134038 discloses a method for producing a polymer blend having at least two different propylene-based polymers produced in parallel reactors. The multi-modal polymer blend has a Mw of about 10,000 g/mol to about 150,000 g/mol. U.S. Provisional Application No. 61/892,826, filed on Oct. 18, 2013, discloses an adhesive composition for nonwoven applications having 50-80 wt % of the polymer blend disclosed in International Publication No. 2013/134038 and any selection of tackifier.
Although many different types of polymers are known and have been used in HMA formulations, there remains a need for a tackified adhesive formulation that has high loading of the new base polymers to achieve equivalent or better adhesive performance attributes including stable adhesion over time indicative of broad application temperature ranges, and machine coatability, as compared to HMA formulations that are currently available.